Authentication algorithms for video images

ABSTRACT

A method of authenticating a video image created by a camera (V) or similar video device. The image is formed into a first 2-dimensional pixel array (A1) with each pixel (p m ,n) represented by a data word of a predetermined length. This formatted array is converted into a second 2-dimensional array (A2) which may be made smaller than the first array by eliminating rows and columns from the formatted array. A first linear vector (A3) is created using the data words in the second array, and a second linear vector (A4) is created by repositioning the data words from the first linear vector in a random pattern. A checksum is created by summing the contents of all of the data words in the second linear vector beginning at a location established by a pre-established formula. A header (H) is formed using the resulting checksum, information identifying the device used to create the image, and the time the image is formed. The header is attached to the formatted image and is transmitted and stored with the formatted image to subsequently authenticate the contents of the original image.

CROSS-REFERENCE TO RELATED APPLICATIONS

The subject matter contained in this application is related to U.S.patent applications Ser. No. 08/772,595, filed Dec. 23, 1996;08/772,731, filed Dec. 23, 1996; and Ser. No. 08/771,991, filed Dec. 23,1996.

This application is related to U.S. patent application Ser. No.08/772,595 filed Dec. 23, 1996 entitled REJECTION OF LIGHT INTRUSIONFALSE ALARMS IN VIDEO SECURITY SYSTEM; U.S. patent application Ser. No.08/772,731, filed Dec. 23, 1996 entitled LOW FALSE ALARM RATE DETECTIONFOR VIDEO IMAGE PROCESSING BASED SECURITY ALARM SYSTEM; and U.S. patentapplication Ser. No. 08/771,991, filed Dec. 23, 1996 entitled REDUCTIONIN FALSE ALARM OF IMAGE PROCESSING BASED SECURITY SYSTEM BY PERFORMINGCLASSIFICATION OF OBJECTS DETECTED.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

This invention relates to the authentication of visual images such asare produced by a video camera or the like, and more particularly to amethod of authentication employing algorithms to encode information bywhich the image can be authenticated.

There are a variety of situations in which it is important to know thata visual image such as an image transmitted from one location toanother, or a stored image which is to be used at a later time isprovided or maintained in the exact form in which it was produced. Inthe medical field, for example, it is now commonplace to transmit apicture (a visual image) of a patient from one site (a local hospital,for example) to another (the location of a specialist). The image may bean x-ray, CAT scan image, or other image of the patient. Because theimage may be used in making a diagnosis, describing a medication orcourse of treatment, or viewed by a specialist while surgery is beingperformed, any inaccuracies in the received image can potentially haveserious consequences. And, it is known that transmission errors due tonoise on the transmission line, temporary disruptions, etc. do occur.

As a further example, many police interrogation rooms are equipped withvideo equipment so the police examination of a suspect can be recorded.The resulting record can then be used for evidentiary purposes, as wellas to defend the police against charges by a suspect that he wasmistreated or that a confession was forced from him.

In security systems, to use another example, a video system may capturethe image of an intruder during an unauthorized entry. The imagetherefore can become part of the evidence which is used to prosecute asuspect. To use the image as evidence against the suspect at trial, itis necessary to maintain the image in its original form and do so in away that the custodian of the evidence can clearly demonstrate to acourt that the image has not been tampered with. It is well known thattechnology exists by which images can be modified. Such technology canbe used to alter the image in such a way that its evidentiary value isdestroyed. It is thus important to provide a foolproof method by whichtampering can be prevented, or if tampering occurs, it is readilydiscernible.

BRIEF SUMMARY OF THE INVENTION

Among the several objects of the present invention may be noted theprovision of a method of authenticating visual images so to preventtampering with the image, or if the image is transmitted from onelocation to another, to make it easy to determine if the image which wasreceived exactly corresponds with that which was transmitted;

the provision of such an authentication method in which datarepresenting the content of the whole or a portion of the image isencrypted at the time the image is produced with this encrypted portionof the image being maintained with the entire image for subsequentauthentication of the image;

the provision of such a method in which the encryption of the portion ofthe image is accomplished using an algorithm that has as a factorelements of the time at which the image is produced, these elementsincluding the month, day, hour, and minute at which the image isproduced;

the provision of such a method in which the image content encryptioncode changes minute by minute, so the results from the encryption of animage at one minute produces an authentication code which is differentfrom the authentication code which would result if the encryption weremade a minute earlier or a minute later;

the provision of such a method by which, once the image isauthenticated, if the image subsequently tampered with, or otherwisealtered, such tampering or alteration is not only immediatelydiscernible, but the portion of the image which has been tampered withor altered can be readily identified;

the provision of such a method by which the visual image is converted toa data format arranged in a first array and subsequently processedthrough successive arrays or linear vectors as part of the encryptionprocess;

the provision of such a method in which a checksum value is ultimatelyderived for the processed image, the checksum value then being placed ina header attached to the original image, the image and header then beingstored or transmitted together so the checksum information can be usedto provide image authentication;

the provision of such a method to further include in the headerinformation as to where the image was taken and the time at which theimage was formed;

the provision of such a method in which encryption codes used in thealgorithm used can be varied from one location to another, and in whichthe codes are periodically changed;

the provision of such a method which is useful, for example, intransmitting pictorial medical information from one location to anotherto verify that an image which is received corresponds with thattransmitted, or in a security system for monitoring a facility anddetecting a breach in security at the facility, especially whereevidence of the breach is captured by a camera and it is important tosubsequently authenticate the image produced for use by law enforcementofficials, or in court; and,

the provision of such a method in which the algorithm used for producingthe authentication is readily incorporated in image processing equipmentlocated at the site where images are produced so authentication for theimage can be created when the image is produced.

In accordance with the invention, generally stated, a method is taughtfor authenticating a video image created by a camera or other videodevice. The visual image is transformed into a data format with a2-dimensional array being created in which each pixel forming the imageis represented by a data word of predetermined length. This array may beconverted into a second 2-dimensional array of a size different thanthat of the first array to reduce the required data transmission rate.This is not an essential part of the algorithm but may simply be apractical necessity. It will be understood that the algorithm works forall pixel formats (512×480, 384×288, etc.). This conversion is performedusing a set of rules by which certain rows and columns in the formattedarray are eliminated. A first linear vector is now formed and includesthe data words transferred from the first to the second 2-dimensionalarray. A second linear vector is formed by rearranging the data words inthe first linear vector, the new locations of the data words in thesecond linear vector being randomly selected. A checksum is determinedusing the data words as arranged in the second linear vector. A headeris created using the resulting checksum, information identifying thedevice used to create the visual image, and the time the visual image isproduced. This header is attached to the formatted array. Other objectsand features will be in part apparent and in part pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the drawings, FIG. 1 represents a facility where a security systemutilizing the image encoding and authentication method of the presentinvention is installed as an example of the usefulness of the method;

FIG. 2 is a simplified block diagram of an image processing system inwhich the authentication process is employed;

FIG. 3 is a representation of the steps performed in accordance with themethod to produce an image authentication;

FIG. 4 illustrates a 2-dimensional arrangement of data wordsrepresenting pixels forming the visual image;

FIG. 5 illustrates a linear vector formed by converting a 2-dimensionalarray;

FIG. 6 illustrates a portion of the process by which a checksum isproduced for image authentication;

FIG. 7 is a simplified representation of a header which is created usingthe checksum and information relating to the time and place the imagewas produced;

FIG. 8 is a simplified representation of the resulting authenticatedimage; and,

FIG. 9 illustrates the steps performed in carrying out a second form ofthe method of the invention.

Corresponding reference characters indicate corresponding partsthroughout the drawings.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings, the method of the present invention is usedto authenticate a visual image which may be produced in any of a numberof different circumstances. For example, a facility F employs a securitysystem 10 to detect the presence of an intruder I who may enter thefacility through a door D or window W. The security system employs animaging means which is represented in FIG. 1 by video cameras V1-V3. Thecameras are strategically located throughout the facility to capture animage of an intruder when facility security is breached. In FIG. 2,security system 10 is shown to include a processing means 12 forprocessing any image captured by a camera V. If it is determined animage from a camera includes that of an intruder, it becomes importantto process the image so the intruder's identity can be determined. It isalso important that the image be authenticated so if it is stored forlater use, or transmitted to the authorities, it can be immediatelydetermined that the image is authentic, or if not, where an alterationto the image has occurred. This is important for evidentiary purposes.Those skilled in the art will recognize other situations in which imageauthentication is useful. For example, as previously mentioned, it isnow common to transmit visual images of a patient from one place toanother for diagnostic purposes, for example. Using the method of thepresent invention, any transmission errors caused for whatever reason,can be immediately ascertained. This prevents the integrity of atransmitted image from being comprised. The method of the presentinvention provides a unique process by which image authentication isachieved. Further, the encryption techniques employed in carrying outthe process result in the authentication of an image which will bedifferent at one time from another.

Referring to FIG. 3, the original image captured by a camera V comprisesa plurality of individual pixels. Each pixel can be converted into adata word, for example, a 6-bit data word. The data words can thenarranged into a 2-dimensional formatted array having m rows r and ncolumns c. A 2-dimensional array of 480 rows and 512 columns isdesignated A1 in FIG. 3. Designations for the pixel locations start atthe upper left corner of the array, and proceed across and down thearray to the lower right. The value of a pixel in the array at aposition m,n is given by p_(m),n with the upper left pixel in the arraybeing designated p₀,0, and the pixel in the lower right p₄₇₉,511.

In accordance with the invention, array A1 representing the originalimage is first converted into a second and, if necessary for datareduction, smaller array A2. In FIG. 4, array A1 is shown to include aplurality of rows r₁, r₂, . . . r_(m-1), R_(m), and a plurality ofcolumns C₁, c₂, . . . c_(n-1), C_(n). In converting from array A1 toarray A2, the process involved may require the elimination of rows andcolumns from array A1 in accordance with a set of rules. One such set ofrules may be:

a) eliminate the even numbered rows if the hour at which the image isformed is an even numbered hour;

b) eliminate the odd numbered rows if the hour at which the image isformed is an odd numbered hour;

c) eliminate the even numbered columns if the day of the month at whichthe image is formed is an even numbered day; and,

b) eliminate the odd numbered columns if the day of the month at whichthe image is formed is an odd numbered day.

In accordance with these rules, the resulting array A2 will be a 240×2562-dimensional array in which the constituent data words included in thearray will change from one hour to the next. Further, it will beappreciated that the rules can use other elements for the measure oftime (hours and minutes), and also that the rules can require othermanipulations beside the elimination of every other row or column. Thismeans that array A2 could be a larger or smaller array than the 240×256array shown in FIG. 3.

Once array A1 is converted into array A2, the next step is to convertarray A2 into a linear vector A3. This is done by concatenating the datawords in the array so they are now arranged linearly as shown in FIG. 5.The first element in linear vector A3 comprises the 6-bit data word forthe first pixel p₀,0 in array A2. The next pixel is p₀,1, then p₀,2, andso forth through to pixel P239255. The resulting vector has a vectorlength of 61,440 data words (240*256).

Linear vector A3 is next transformed into a second linear vector A4. Asindicated by the arrows in FIG. 3, the locations of the data words areshuffled so the locations they occupy in array A4 is unique and isdetermined in accordance with a look-up code provided to processingmeans 12. According to the code, vector locations in vector A3 arerandomly redistributed in vector A4. The position shuffling code ischanged on a periodic basis which can be monthly, daily, hourly, or bythe minute. As a result, the location of the same words transferred fromvector A3 into vector A4 will be different from one time to another.

After forming vector A4, the method next includes the calculation ordetermination of a checksum for the data words as they are now arrangedin this vector. In performing the checksum, a location on the linearvector is selected as a starting location. The location selection isdone using a formula which incorporates elements of the time at whichthe image is formed. Again, these can include the month, day, hour, andminute at which the image is produced, or a combination of the elements.Each of these four time elements may, for example, have a value ascribedto it. The elements are then combined in a predetermined manner. Thatis, one element may be added to, subtracted from, multiplied with, ordivided by another element. Constants can also be used with theelements. Those skilled in the art will appreciate that a wide range ofcombinations are possible without departing from the scope of theinvention. If minutes, for example, are used in the formula, then astarting location determined in accordance with the formula will changeminute by minute. Accordingly, the starting location selected in arrayA4 at one minute will be different from that which is selected the nextminute.

Referring to FIG. 3, the location in array A4 where a checksumdetermination starts is indicated. As indicated by the Fig., apredetermined block B1 of words, 256 for example, is selected and theircorresponding bit values sequentially summed. After the first summationis complete, a second predetermined block B2 is taken and the processrepeated. As shown in FIG. 6, the checksum determination includes taking256 consecutive data words DW1-DW256 from array A4. The most significantbits of each data word are summed together to produce a value Σmsb. Theprocess is repeated for each column of bits until the sum of the leastsignificant bits Σlsb is calculated. Each summation is used to form 6new data bytes for the respective summation values. Because array A4includes 240 blocks B1-B240 each having 256 data words, at the end ofthe checksum process, a sequence of 1,440 bytes (240*6) will have beenproduced. These bytes now represent an encrypted value of the contentsof the original image.

A second checksum is derived by taking the first value previously chosenand adding the bits from the next 256 entries further along (i.e., thefirst entry in the next block in array A4) and continuing the summationfor all 240 blocks of data words. Then starting at the next entry of theoriginal block, another checksum is found. This process is continueduntil all entries in the block are exhausted, and will result in anadditional 256×6 checksum.

Next, a header H is formed using the checksum values and informationrelating to the camera which produced the image and the time (month,day, hour, and minute) at which the image was formed. As shown in FIG.7, header H has two parts. The first part HP1 includes the camera andtime reference information. The second part HP2 includes the 1440checksum bytes. It will be understood that the information relating tothe camera identification and time reference will comprise a pluralityof bytes and the location of these bytes may be scrambled within headerpart HP1. It will further be understood that the values for therespective time elements may again be mathematically combined so a monthvalue, for example, may be added, subtracted, multiplied, or divided bya constant value. After the header is formed, it is attached to theinitial image array to form a completed authenticated image AI (see FIG.8). As shown in FIG. 2, this authenticated image is what is supplied byprocessing means 12 to transmission or storage means 14.

Since header H includes time information about when the image wasproduced, this information, together with the checksum value can be usedto authenticate the image at a later time or different place. If theauthentication reveals that the image content is not that of theoriginal image, the location where a change has occurred is determinedfrom by reference to the checksum. Since the formatted image array is a2-dimensional array, any change in the content will effect values forboth the row and column where the change occurs. The checksum value isderived from the information content in the original array, and soincorporates both row and column values. Reference to the checksum willtherefore locate where within the array a content value has changed. Itwill be appreciated that because of all the possible authenticationcombinations which can result from use of the process, that it isvirtually impossible for someone to be able to intentionally change thecontent value of the image in a way that will not be detected.

Referring to FIG. 9, a second manner for carrying out the method of theinvention includes converting the original image array A1 to a secondarray A2, as before, with the rows and columns which are eliminatedbeing determined in accordance with an established set of rules. Now,instead of converting 2-dimensional array A2 into a linear vector, athird 2-dimensional array A5 is created in which the rows and columnsare shuffled in a random sequence. The code by which this shufflingoccurs is again periodically changed so that the repositioning whichresults at one time differs from that which occurs at another. Thus, inarray A5, the first pixel no longer is the pixel p₀,0, but rather apixel p_(mx),ny ; and the last pixel no longer pixel p₂₃₉,255, but apixel p_(ma),nb. A checksum is again created, this time by calculatingchecksums for the rearranged rows and columns in array A5. The locationwithin the array where the checksum determination starts is again basedupon a formula which include values representing elements of the timethe image is produced. The result is that the location in the arraywhere the checksum starts will be different for one time at which animage formed to another. Once the checksum has been completed, a headerH similar to that shown in FIG. 7 is formed. The first portion HP1 ofthe header again includes location and time information about the imageand the second portion HP2 the checksum vector. The header is attachedto the original image array A1 to produce the authenticated image AI.

This second way of carrying out the method of the invention also has theadvantage of authenticating the image at a later time and also ofallowing immediate determination of whether and where a change incontent of the original image has occurred. Further, this approach hasthe advantage of requiring only 496 words (240+256) to be processedrather than the 61,440 words required in executing the method aspreviously described.

What has been described is a method of authenticating visual images toverify that the content of an image viewed at a later time is the sameas that when the image was produced. Or, if the image content haschanged, this is readily detected as well as the location within theimage where a change has occurred. The image is encrypted at its sourceand the authentication remains with the image regardless of itssubsequent use. For this purpose, the algorithm used to produce theauthenticated image is incorporated in image processing equipmentlocated at the site where the image is produced and authenticationoccurs at the time the image is produced. Authentication is accomplishedby an algorithm which may include as one factor elements of the time atwhich the image is formed. These elements includes the month, day, hour,and minute at which the image is created. Because encryption can changeon a basis of time, an authentication code for an image at one time willbe different from an authentication code for the same image made at adifferent time. Also, because of the range of combinations which canpossibly be used to authenticate an image it is virtually impossible fora change in image content to go undetected. The method is useful in awide range of applications where it is image content be must be verifiedat a different time or place from those where the image is created.

In view of the foregoing, it will be seen that the several objects ofthe invention are achieved and other advantageous results are obtained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

Having thus described the invention, what is claimed and desired to besecured by Letters Patent is:
 1. A method of authenticating a videoimage by forming the image into a data format, encrypting a portion ofthe formatted image, and attaching the encrypted portion to the originalimage so the content of the original image can thereafter beauthenticated by reference to the encrypted portion thereof, saidformatted image comprising a 2-dimensional array of pixels each of whichis represented by a data word of a defined length and the methodincludes converting the formatted image from said 2-dimensional arrayinto a second 2-dimensional array.
 2. The method of claim 1 furtherincluding detecting any modification to the content of the originalimage and determining where in the image the modification occured. 3.The method of claim 1 further including forming a header for theformatted image using the encrypted portion thereof, attaching theheader to the formatted image, and storing or transmitting the headerwith the formatted image for authenticating the image.
 4. The method ofclaim 1 wherein forming the second 2-dimensional array includesmanipulating the rows and columns of the formatted array by a set ofrules which incorporate the time at which the original image is formed.5. The method of claim 4 further including converting the second2-dimensional array into a linear vector by concatenating the data wordscontained in the second array.
 6. The method of claim 5 furtherincluding converting the aforesaid linear vector into a second linearvector in which the position of the data words in the first linearvector are located at different positions in the second linear vector,the positioning of the data words in the second linear array beingdetermined in accordance with a predetermined code by which the datawords are randomly positioned in the second linear vector.
 7. The methodof claim 6 further including determining a checksum using the data wordsas arranged in the second linear vector, the checksum determinationbeginning at a location in the second linear vector which is establishedby a formula in which values representing elements of the time at whichthe image is formed are included.
 8. The method of claim 7 whereindetermining the checksum includes successively summing the values ofeach of the bits comprising a predetermined number of data words, thesummation beginning with the most significant bit in each data word andproceeding through to the summation of the least significant bitthereof.
 9. The method of claim 8 wherein determining the checksumfurther includes computing a checksum for blocks of data words each ofwhich comprises the predetermined number of data words until a checksumis produced which includes all the data words in the second linearvector.
 10. The method of claim 8 further including forming a headerwhich is attached to the formatted array, one portion of the headerincluding data words representing the checksum value for the data wordscontained in the second linear vector, the checksum value contained inthe header being used to authenticate the contents of the formattedimage.
 11. The method of claim 10 wherein another portion of the headeris formed by combining information relating to an identity and locationof a device used to form the image, and the time at which the image isformed.
 12. The method of claim 3 wherein the operations performed inproducing the authentication are incorporated in an algorithm, portionsof the algorithm including values representing elements of the time atwhich the image is formed, the values of the time elements periodicallychanging whereby an authentication for a formatted image produced at onetime would be different from the authentication for the same formattedimage if produced at a different time.
 13. The method of claim 4 furtherincluding repositioning the rows and columns in the second array, therepositioning being determined in accordance with a predetermined codeby which the rows and columns are randomly repositioned into a third2-dimensional array.
 14. The method of claim 13 further includingdetermining a checksum for the third array by successively summing thevalues of the bits forming the data words for each row and column of thethird array, the summation beginning by summing all of the mostsignificant bits in the data words and proceeding through to the leastsignificant bits thereof, the checksum determination beginning at alocation in the third array established by a formula in which valuesrepresenting elements of the time at which the image is formed areincluded.
 15. The method of claim 14 further including forming a headerwhich is attached to the formatted array, one portion of the headerincluding data words representing the checksum value for the data wordvalues contained in the third array, the checksum value contained in theheader being used to authenticate the contents of the formatted image.16. The method of claim 15 wherein another portion of the header isformed by combining information relating to an identity and location ofa device used to form the image, and the time at which the image isformed.
 17. A method of authenticating a video image comprising:creatinga video image using a video device; formatting the image created by thedevice into a first 2-dimensional pixel array in which each pixel isrepresented by a data word of a predetermined length; converting thefirst 2-dimensional array into a second 2-dimensional array bymanipulating the rows and columns in the first array; forming a linearvector using the data words in the second array with the location ofdata words being randomly selected; determining a checksum from the datawords in the linear vector; forming a header using the checksum,information identifying the device used to create the image, and thetime at which the image is formed; and, attaching the header to theformatted array representing the original contents of the image for theheader to be stored or transmitted with the formatted array with theinformation contained in the header used to authenticate the image. 18.The method of claim 17 wherein the second array is smaller in size thanthe first array and is formed by eliminating selected rows and columnsin the first array, the rows and columns which are eliminated beingdetermined in accordance with a set of rules incorporating elements ofthe time at which the image is formed.
 19. The method of claim 18further including converting the second array into a first linear vectorby concatenating the data words in the second array.
 20. The method ofclaim 19 further including converting the first linear vector into asecond linear vector in which the position of the data words in thefirst linear vector are located at different positions in the secondlinear vector, the positioning of the data words in the second lineararray being determined in accordance with a predetermined code by whichthe data words are randomly positioned in the second linear vector. 21.The method of claim 20 wherein determining the checksumincludes:selecting a predetermined number of consecutive data words inthe second linear vector; summing the contents of the data wordsbeginning by summing all of the most significant bits in the data wordsand proceeding through to the least significant bits; and, computing achecksum for blocks of data words each of which comprises thepredetermined number of data words until a checksum is produced whichincludes all the data words in the second linear vector, the location inthe second linear vector where the checksum determination begins beingestablished by a formula in which values representing elements of thetime at which the image is formed are included.
 22. The method of claim21 wherein the location in the second linear vector where the checksumdetermination begins is a function of the month, day, hour, and minuteat which the image is formed.
 23. The method of claim 21 wherein formingthe header includes:forming a first portion of the header by combiningtogether information relating to an identity and location of a deviceused to form the image, and the time at which the image is formed; and,forming a second portion of the header including the checksum value forall the data words in the second linear vector.
 24. A method ofauthenticating a video image comprising:creating a video image using avideo device; formatting the video image into a 2-dimensional pixelarray in which each pixel is represented by a data word of apredetermined length; converting the formatted array into a second2-dimensional array by manipulating the rows and columns forming theformatted array; determining a checksum from the data words forming thesecond array; forming a header using the checksum, informationidentifying the device used to create the image, and the time at whichthe image is formed; and, attaching the header to the formatted arrayand storing or transmitting the header with the formatted array toauthenticate the content of the original image as stored in theformatted array.
 25. The method of claim 24 wherein the second array issmaller in size than the formatted array and is formed by eliminatingselected rows and columns in the formatted array, the rows and columnswhich are eliminated being determined in accordance with a set of rulesincorporating elements of the time at which the image is formed.
 26. Themethod of claim 25 further including repositioning the rows and columnsof the second array into a third 2-dimensional array, the repositioningbeing determined in accordance with a predetermined code by which therows and columns are randomly repositioned into the third array.
 27. Themethod of claim 26 wherein determining the checksum for the third arrayincludes successively summing the values of the bits forming the datawords for each row and column of the third array, the summationbeginning by summing all of the most significant bits in the data wordsand proceeding through to the least significant bits thereof, thechecksum determination beginning at a location in the third arrayestablished by a formula in which values representing elements of thetime at which the image is formed are included.
 28. The method of claim27 wherein forming the header includes:forming a first portion of theheader by combining together information relating to an identity andlocation of a device used to form the image, and the time at which theimage is formed; and, forming a second portion of the header includingthe checksum value for all the data words in the third array.
 29. Amethod of authenticating a video image comprising:creating a video imageusing a video device; formatting the image created by the device into afirst 2-dimensional pixel array in which each pixel is represented by adata word of a predetermined length; converting the first 2-dimensionalinto a second 2-dimensional array which is a smaller array than thefirst array, the conversion from the first to the second 2-dimensionalarray being performed by eliminating rows and columns from the firstarray in accordance with a set of rules incorporating elements of thetime at which the image is formed; converting the second array into alinear vector by which the position of the data words is determined inaccordance with a predetermined code by which the data words arerandomly positioned in the linear vector; determining the checksum forthe image by summing the contents of all of the data words in the linearvector beginning at a location established by a formula in which valuesrepresenting elements of the time at which the image is formed areincluded; forming a header using the resulting checksum, informationidentifying the device used to create the image, and the time at whichthe image is formed, and; attaching the header to the formatted arrayrepresenting the original contents of the image for the header to bestored or transmitted with the formatted array with the informationcontained in the header used to authenticate the image.
 30. A method ofauthenticating a video image comprising:creating a video image using avideo device; formatting the video image into a 2-dimensional pixelarray in which each pixel is represented by a data word of apredetermined length; converting the formatted array into a second2-dimensional array by eliminating selected rows and columns in theformatted array, the rows and columns which are eliminated beingdetermined in accordance with a set of rules incorporating elements ofthe time at which the image is formed; repositioning the rows andcolumns of the second array into a third 2-dimensional array, therepositioning being determined in accordance with a predetermined codeby which the rows and columns are randomly repositioned into the thirdarray; determining a checksum for the image by summing the contents ofall of the data words in the third array beginning at a locationestablished by a formula in which values representing elements of thetime at which the image is formed are included; forming a header usingthe checksum, information identifying the device used to create theimage, and the time at which the image is formed; and, attaching theheader to the formatted array and storing or transmitting the headerwith the formatted array to authenticate the content of the originalimage as stored in the formatted array.